1. Technical Field
A variety of different web tensioning control devices have been developed to control the web tensioning of material during production and use. Given variations in material yield, it is necessary to maintain an even tension on the web for a constant end product or application.
2. Description of Prior Art
Prior art devices of this type have relied on a variety of different structures to sense and control web tension dependent on the industry and end use and production, see for example U.S. Pat. Nos. 4,146,190, 3,241,785, 4,407,331, 4,696,439, 4,775,086, 4,838,498, 4,993,660.
In U.S. Pat. No. 3,241,785 an apparatus and process for winding under varying tension is disclosed in which the actual tension of the web is sensed by hydraulic means and pneumatic feedback means are used to develop correcting signals that is sent to the final control element.
In U.S. Pat. No. 4,146,190 a web winding control system can be seen having a variable torque output motor controlled by a spring biased dancer roller. The dancer roller pivots on a swinging arm with the relative movement of the roller denoting variations in web tension which accordingly controls output of a control motor transporter.
In U.S. Pat. No. 4,407,331 is directed towards a speed regulator for the warp beam of a weaving machine. The device uses two optical incoders to determine the speed of the web or fiber entering and leaving the tensioning ruler. The tension is induced by the pull of a spring with the tension determined by a combination of a signal from the speed of the incoders and the position of the potentiometer.
In U.S. Pat. No. 4,696,439 a tape speed and tension control system for a magnetic cassette apparatus is disclosed in which a tape speed signal is generated by a speed sensor driven by the speed sensing ruler, a closed loop servomechanism controls a pair of drive motors coupled directly to respective cassette hubs to regulate and maintain constant tape speed.
In U.S. Pat. No. 4,775,086 a take-out/take-up tension control apparatus is disclosed for use in stretched film or sheet production line. The device uses a dancer roller which is used to control the force applied thereto so that accurate tension can be read and maintained. When correction of tension is required, selective forces apply to the dancer roller by displacing same absorbing tension variation.
U.S. Pat. No. 4,838,498 is directed to a web tensioning system using a dancer roller that pivots circumferentially in response to tension changes. A hydraulic control cylinder interconnected to said roller arms imparts relative position implying control values to motorized regulator.
In U.S. Pat. No. 4,993,660 a reel drive device is disclosed utilizing a detector for detecting a rotating state of a reel, data for control holding device for holding data for control of the rotational drive and an output control circuit for causing the data for control holding device to output the data for control of the rotational drive in response to the rotational state of a reel detection in the detector and a drive control circuit for controlling the drive state of the rotational drive in response of the data for control of the rotational drive.
Additionally, tension control devices are known in the art as is evidenced by the publication "New "2000" Series Tension Control For Filament Winding".
This publication describes a tension control system for fibers utilizing full digital control for analysis interpretation of the tension monitor used in association with a network management system, a PC computer and computerized digital control instructions for accurately determining the tension on a filament by a software control.
Such digital tension control devices are complicated, expensive and are primarily used with multiple computer controlled fiber winding and unwinding systems used in a variety of processes and applications in industry.